# 5. Description of the parameters in PION parameter files¶

divide up parameters by topic and describe them in tables.

## 5.1. Stellar Winds¶

Stellar winds in PION are implemented in 3 modules: a constant wind, an evolving wind, and a latitude-dependent wind. The parameter file for a constant wind has a number of parameters that should be set, quoted below with the expected units. They are stored in these units in the SWP struct of type stellarwind_params.

Parameter Description Units/values
WIND_[i]_pos[n] Star position $$n\in[0,1,2]$$ cm
WIND_[i]_type [Constant, evolving, latitude dependent] [0,1,2]
WIND_[i]_mdot Mass-loss rate from star (dot{M}) $$\mathrm{M_{\odot}\,yr}^{-1}$$
WIND_[i]_vinf Terminal velocity of wind $$\mathrm{km\,s}^{-1}$$
WIND_[i]_vrot Equatorial rotation velocity $$\mathrm{km\,s}^{-1}$$
WIND_[i]_temp Effective Temperature of star, $$T_\mathrm{eff}$$ K
WIND_[i]_TR[n] Value of tracer $$n$$ in wind Usually $$\in [0,1]$$
WIND_[i]_enhance_mdot ad-hoc flag to increase $$\dot{M}$$ Default is 0
For constant winds, these data are stored in the global struct SWP, defined in pion/source/constants.h, using these units. In simulation snapshots they also have the same units. The evolving wind file should have all units in CGS.